This invention relates to measuring instruments and methods and is particularly directed to instruments and methods used to measure the size and dimensions of heart valves in the surgical operating room at the time of heart valve reconstruction or replacement.
When a surgeon must replace one or more of a patient""s heart valves because of disease or defect of the native valve(s), the surgeon must identify the diameter of the patient""s annulus in order to select the correct size replacement heart valve. The measurement of heart valve diameter in the operating room is typically done with some type of plug gauge. Gradated sizes of plug gauges, typically in 2 millimeter increments are used to find the best fit for any given valve annulus. The advent of homograft valves and, more recently, methods for reconstructing heart valves, makes it desirable to determine more than simply the best fit diameter. For operations involving the use of homograft valves, stentless heterograft valves, and any one of several methods of aortic or pulmonic heart valve reconstruction being used, it is also desirable to measure the height of the leaflets and the symmetry, or lack thereof, of the valve commissures. To meet these requirements, an instrument and methods have been developed that can be used in the operating room to assess valve geometry more completely than has been possible in the past.
The present invention is comprised of methods and instruments that can be used to measure the diameter of the valve annulus at the commissural level, to compare the height and lines of attachment of the individual leaflets with reference to a normalized geometry, and to determine the symmetry of the valve commissures. One preferred embodiment of the present invention comprises a circular piece with three equally spaced radial spokes that converge in the center to a socket to which a handle can be attached. Curved legs that correspond to the geometry of the normal native valve leaflet anatomy, as described in published medical articles, are attached to the circular piece.
In a typical operation to replace or to reconstruct an aortic or pulmonic valve, the diseased native valve is removed down to the annulus of the valve. After this has been done, the valve is sized. With the present invention, sizers of graded dimensions are used until the best-fit diameter at the commissural level is determined. With that sizer inserted in the aortic or pulmonic root, the height of each leaflet from its base to the apex of its commissures can be compared with the expected dimensions for that valve, based on published dimensions. The symmetry of the valve can be judged by aligning any given radial spokes of the circular piece with one commissure, and then noting the spacing of the remaining two commissures. The radial spokes each have a width that corresponds to an arc of the circle that encompasses the normal expected variation from perfect symmetry. Deviations from expected normal leaflet height or symmetry can be readily appreciated and used to increase the precision of the planned surgical procedure.